Spontaneous synthesis of gold nanoparticles on gum arabic-modified iron oxide nanoparticles as a magnetically recoverable nanocatalyst

A novel magnetically recoverable Au nanocatalyst was fabricated by spontaneous green synthesis of Au nanoparticles on the surface of gum arabic-modified Fe₃O₄ nanoparticles. A layer of Au nanoparticles with thickness of about 2 nm was deposited on the surface of gum arabic-modified Fe₃O₄ nanoparticles, because gum arabic acted as a reducing agent and a stabilizing agent simultaneously. The resultant magnetically recoverable Au nanocatalyst exhibited good catalytic activity for the reduction of 4-nitrophenol with sodium borohydride. The rate constants evaluated in terms of pseudo-first-order kinetic model increased with increase in the amount of Au nanocatalyst or decrease in the initial concentration of 4-nitrophenol. The kinetic data suggested that this catalytic reaction was diffusion-controlled, owing to the presence of gum arabic layer. In addition, this nanocatalyst exhibited good stability. Its activity had no significant decrease after five recycles. This work is useful for the development and application of magnetically recoverable Au nanocatalyst on the basis of green chemistry principles.     

Recyclable Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@Tween20@Ag Nanocatalyst for Catalytic Degradation of Azo Dyes

Silver nanoparticles supported on superparamagnetic iron oxide (SPION)-Tween20 nanocomposite were prepared by a combined polyol and chemical reduction routes. The morphology, composition and structure of Fe₃O₄@Tween20@Ag nanocatalyst were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy, energy dispersive X-ray spectroscopy, thermal gravimetric analyzer, and X-ray powder diffraction. In addition the magnetic properties were evaluated with vibrating sample magnetometry. It was found that Fe₃O₄@Tween20@Ag nanocatalyst could catalyze the degradation of various organic azo dyes and could easily be recovered from the reaction medium with external magnet. Also, the magnetic catalyst can be succesfully recycled and reused for at least five successive degradation cycles of methyl orange, methylene blue and Rhodamine B, confirming a high recycling efficiency. The cost effective and recyclable Fe₃O₄@Tween20@Ag nanocatalyst provide an novel nanomaterials architecture for environmental remediation applications.     

Amine-Functionalized Silica-Supported Magnetic Nanoparticles: Preparation,Characterization and Catalytic Performance in the Chromene Synthesis

An efficient, one-pot multicomponent procedure for good to excellent yield preparation of 2-amino-4H-chromene-4-carboxylate and 2-amino-5H-pyrano[3,2-c]chromene-4-carboxylate using Fe₃O₄@SiO₂–NH₂ nanoparticles as a facile synthesized, easily recoverable, heterogeneous catalyst was investigated. The amine-functionalized silica-supported magnetic catalyst was characterized successfully by Fourier transforms infrared spectroscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy analyses. Using ethanol as a green solvent in these multicomponent reactions and no significant decrease in catalytic activity of the nanocatalyst during recovering process are other major points in this worthy chromene derivatives synthesis.     

Silica-modified magnetite Fe3O4 nanoparticles grafted with sulfamic acid functional groups: an efficient heterogeneous catalyst for the synthesis of 3,4-dihydropyrimidin-2(1H)-one and tetrahydrobenzo[b]pyran derivatives

Silica-modified magnetite-polyoxometalates functionalized with sulfamic acid groups as hybrid nanoparticles were prepared by sulfonation of diamine-functionalized propyl group grafted on the magnetic silica-coated Fe₃O₄ nanoparticles. This heterogeneous nanocatalyst was explored to present high catalytic performance for the synthesis of 3,4-dihydropyrimidinones and tetrahydrobenzo[b]pyrans under mild reaction conditions. The properties of this nanocatalyst were characterized by FT- infrared, energy-dispersive X-ray spectrum, scanning electron microscope, X-ray diffraction, X-ray fluorescence and elemental analysis. Easy separation of the nanocatalyst by using an external magnet, recyclability, non-toxicity, versatility and high stability of the catalyst combined with low reaction times and excellent yields make the present protocol very useful and attractive for the synthesis of the titled products.     

Synthesis,characterization and heterogeneous catalytic activity of diamine-modified silica-coated magnetite-polyoxometalate nanoparticles as a novel magnetically-recoverable nanocatalyst

Magnetite-polyoxometalate hybrid nanomaterials, Fe₃O₄@SiO₂@NH-NH₂-PW, was prepared by grafting of H₃PW₁₂O₄₀ on the diamine-functionalized Fe₃O₄ magnetite nanoparticles. This new heterogeneous nanocatalyst demonstrated a catalytic performance in the synthesis of tetrahydrobenzo[b]pyrans and Knoevenagel condensation in aqueous media. The nanocatalyst could easily be separated from the reaction solution by using an external magnet and recycled several times. The recovered catalyst was reused for at least seven runs without significant loss in catalytic activity. The resulting nanomaterials were characterized with different physicochemical techniques, such as Fourier transform infrared (FT-IR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), powder X-ray diffraction (XRD), energy dispersive X-ray analysis (EDAX), thermogravimetric analyze (TGA) and alternating gradient force magnetometer (AGFM). SEM and TEM analyses indicated that nanoparticles had relatively uniform spherical nanoparticles and the average size of Fe₃O₄@SiO₂@NH-NH₂-PW was approximately 60 nm.     

Amino Functionalized Nano Fe3O4@SiO2 as a Magnetically Green Catalyst for the One-Pot Synthesis of Spirooxindoles Under Mild Conditions

(3-Aminopropyl)-triethoxysilane attached to Fe₃O₄@SiO₂ nanoparticles has been characterized by powder X-ray diffraction, vibrating sample magnetometer, scanning electronic microscope, transmission electron microscope, energy dispersive X-ray, thermal gravimetric analysis, and Fourier transform infrared spectroscopy. The prepared nanoparticles employed as a heterogeneous catalyst in the synthesis of spirooxindoles derivatives in one-pot four-component reactions of isatin, methyl cyanoacetate or malononitrile, hydrazine hydrate, and ethyl acetoacetate. Amino-functionalized magnetic nanoparticles showed high catalytic activity in mild reaction conditions and excellent yields of products in short reaction times. Also, this nanocatalyst can be easily recovered by a magnet and reused for subsequent reactions for at least 5 times without noticeable loss in catalytic activity.     

An efficient and recyclable catalytic system for carbon–sulfur coupling reaction and synthesis of 5-substituted 1H-tetrazoles

In this research paper, efficient and economical protocols for the synthesis of symmetrical sulfides and 5-substituted 1H-tetrazoles have been reported using Fe₃O₄@SBTU@Ni(II) as a heterogeneous and recoverable nanocatalyst. The noticeable features of this catalytic system are: operational simplicity, environmentally benign, easier work-up procedure, green and efficient synthetic entry to excellent yield of products in a high reusability and applicability to various starting materials and, therefore, cost efficiency.     

Fe3O4@cellulose composite nanocatalyst: Preparation,characterization and application in the synthesis of benzodiazepines

A cellulose-based nanocomposite with highly loaded Fe₃O₄ nanoparticles was prepared and characterized by Fourier transform infrared spectroscopy (FT-IR) spectra, scanning electron microscopy (SEM) images, energy-dispersive X-ray spectroscopy (EDX) spectra and X-ray diffraction (XRD) measurements. Its catalytic activity was investigated in the condensation reaction between o-phenylenediamines and ketones that produced benzodiazepines in good to excellent yields under mild reaction conditions. A good correlation between the amount of surface acid sites and the morphology of the catalyst and its catalytic activity was observed. The nanocatalyst could be recycled and reused without significant loss of its catalytic activity.     

Novel magnetic nanoparticles-supported inorganic-organic hybrids based on POSS as an efficient nanomagnetic catalyst for the synthesis of pyran derivatives

A new family of polyhedral oligomeric silsesquioxanes with eight triethoxysilane arms (APTPOSS) has been successfully anchored on the surface of Fe₃O₄ nanomagnetics and characterized by infrared spectroscopy, X-ray diffraction spectroscopy, scanning electron microscope, Energy Dispersive Spectroscopy, thermogravimetric analysis, dynamic light scattering and vibrating sample magnetometer. Fe₃O₄@APTPOSS, as a magnetic nanocatalyst for high-yield synthesis of pyrans has been employed.     

Microwave-assisted Fe3O4 nanoparticles catalyzed synthesis of chromeno[1,6]naphthyridines in aqueous media

Fe₃O₄ nanocatalyst was prepared by co-precipitation method and characterized by XRD, FT-IR, TEM, VSM and BET analyses. The particles have an average size of 7 nm and possess highly open mesopores, moderate surface area, and uniform morphology with superparamagnetic behavior. Activity of catalyst was probed through the synthesis of chromeno[1,6]naphthyridines in water under microwave irradiation (MW) and it was about 7-fold higher as compared to conventional method. Nanocatalyst plays a dual role of catalyst as well as susceptor, and enhances the overall capacity to absorb MW. Fe₃O₄ NPs easily recovered by simple magnetic separation and recycled at least 5 times.     

CuI Immobilized on Tricationic Ionic Liquid Anchored on Functionalized Magnetic Hydrotalcite (Fe3O4/HT-TIL-CuI) as a Novel,Magnetic and Efficient Nanocatalyst for Ullmann-Type C–N Coupling Reaction

One of the most important reactions in organic synthesis is Ullmann-type C–N coupling reaction which has been used for preparation of numerous biologically active compounds. In this work, CuI immobilized on tricationic ionic liquid anchored on functionalized magnetic hydrotalcite (Fe₃O₄/HT-TIL-CuI) has been successfully prepared and fully characterized by different techniques, including fourier-transform infrared spectroscopy, vibrating sample magnetometer, thermo gravimetric analysis, transmission electron microscopy, field-emission scanning electron microscopy, energy dispersive X-ray spectroscopy, elemental mapping, zeta potential, X-ray diffraction, temperature programmed desorption of ammonia (NH₃-TPD), temperature-programmed reduction and inductively coupled plasma. The results showed that the as-prepared nanocatalyst possesses plate-like morphology with approximate size of 50 nm and superparamagnetic behavior. Also, total acidity and total hydrogen consumption of the nanocatalyst were measured to be 8.5 and 1.41 mmol g^?1, respectively. This nanocatalyst exhibited favorable performance for C–N coupling reaction among a variety of aryl halides and N(H)-heterocycles (benzimidazoles, pyrazoles and triazoles) in the presence of 2.5 mol% of nanocatalyst without any additives under air atmosphere revealing high yields in all cases. Besides, it is noted that in the present system the desired product can be easily and quickly isolated and nanocatalyst also recovered magnetically from the reaction mixture employing a permanent magnet for at least six consecutive trials without a discernible decrease in catalytic activity which makes the proposed methodology appropriate for industrial. The findings demonstrated the advantages of the present method as no need for neutral atmosphere, appropriate times, recyclability of the catalyst, broad substrate scope, minimization of chemical waste, simple purification of products, easy workup process, and high yields.

     

Protic Ionic Liquid Assisted Synthesis and Characterization of Ferromagnetic Cobalt Oxide Nanocatalyst

Cobalt oxide (Co₃O₄) nanocatalyst was synthesized by sol-gel method using the protic ionic liquid namely 1-butylimidazolium glycolate as solvent and stabilizer. The obtained Co₃O₄ nanocatalyst was characterized by powder X-ray diffraction (XRD), Fourier transform infrared, High resolution scanning electron microscopy (HR-SEM), Energy dispersive X-ray (EDX), High resolution transmission electron microscopy (HR-TEM), Selected area electron diffraction, UV–Visible diffuse reflectance spectroscopy, Photoluminescence spectroscopy, Brunauer–Emmett–Teller surface area and Vibrating sample magnetometer (VSM). Powder XRD results showed the well-crystalline cubic structure of synthesized Co₃O₄ with size of 19.29 nm. Also, the sphere-like morphology of Co₃O₄ nanocatalyst was confirmed by HR-SEM and HR-TEM images. Furthermore, the synthesized Co₃O₄ nanocatalyst possessed optical band gap values of 1.75 and 2.46 eV and hence acted as a semiconducting material. In addition, the presence of small hysteresis loop in Magnetic measurement (VSM) confirmed the ferromagnetic nature of Co₃O₄ nanoparticles. Moreover, the synthesized Co₃O₄ nanocatalyst found to be used in photo-catalytic degradation of methylene blue and exhibited 94.61% efficiency.     

Preparation and structural properties of Fe3O4–polyimide hybrid nanocomposites

Polyimide films in which magnetic Fe₃O₄ nanoparticles are uniformly distributed are prepared. Before the preparation of the Fe₃O₄–polyimide composites, pure magnetite nanoparticles (Fe₃O₄) have been synthesized in water by co-precipitation (from ferric chlorides). Its surface was firstly modified with the 3-aminopropyl triethoxysilane. The prepared polyimide–Fe₃O₄ nanocomposite films were characterized for their structure, morphology, and thermal behavior employing Fourier transform infrared spectroscopy, scanning electron micrograph, X-ray diffraction, and thermal analysis (DTA/TGA/DSC) techniques.     

Sulfonated polystyrene brushes grafted onto magnetic nanoparticles as recoverable catalysts for efficient synthesis of ethyl N-phenylformimidate

In this work, the sulfonated polystyrene brushes were grafted onto magnetic nanoparticles to obtain recoverable catalysts for efficient synthesis of ethyl N-phenylformimidate. First, the surface modification of Fe₃O₄ with a particle size of about 10 nm was performed with the silane coupling agent of vinyl triethoxysilane (SG-151) to obtain Fe₃O₄ with carbon–carbon double bonds on the surface (SG-Fe₃O₄). Subsequently, SG-Fe₃O₄, styrene (St) and chloromethyl styrene (CMSt) were polymerized to obtain the magnetic chloromethylated polystyrene sphere (SG-Fe₃O₄@PS-Cl) with core-shell structure by solution copolymerization. Using St as monomer and SG-Fe₃O₄@PS-Cl as macromolecular initiator, the magnetic polystyrene brush of SG-Fe₃O₄@PS-PSt was obtained by activated regenerated electron transfer catalyst atom transfer radical polymerization. Finally, SG-Fe₃O₄@PS-PSt was sulfonated with sulfuric acid to form a magnetic sulfonated polystyrene brush of SG-Fe₃O₄@PS-PSH. SG-Fe₃O₄@PS-PSH was used as a recoverable acid catalyst to synthesize ethyl N-phenylformimidate. Due to the high loading of the sulfonic acid group of this catalyst, its added amount was lower than other solid acids such as p-toluenesulfonic acid. The results showed that the catalytic performance of SG-Fe₃O₄@PS-PSH was better than p-toluenesulfonic acid and commercial macroporous sulfonic acid resin. The external magnetic field can directly recover SG-Fe₃O₄@PS-PSH, simplifying the recovery of catalyst and reducing the catalyst loss. After recycling, the yield of ethyl N-phenylformimidate was not significantly decreased.     

Magnetically recoverable Fe3O4@SBA-15: An improved catalyst for three component coupling reaction of aldehyde,amine and alkyne

We have synthesized Fe₃O₄ nanoparticles on mesoporous SBA-15 by an “in situ” approach. The synthesized nanocomposite material was well characterized using wide and low angle XRD, N₂ adsorption–desorption isotherm, TEM, FTIR, XPS, and VSM analysis. The Fe₃O₄@SBA-15 nanocomposite material was used as a magnetically recoverable catalyst (MRC) for three component coupling reaction of aldehyde, amine and alkyne. The reported catalyst was recycled up to five times without significant loss in its catalytic activity.     

Cooperative Activation in the Synthesis of Flavanone Antioxidants Using a Simple and Highly Efficient Magnetically Recoverable Nano-Cu-CoFe2O4 Catalyst

ABSTRACT

Double mixed Cu_0.5Co_0.5Fe₂O₄ ferrite nanoparticles were found as a highly efficient and magnetically separable nanocatalyst for the synthesis of varied flavanone antioxidants. A wide range of flavanone derivatives were prepared with excellent isolated yields within the short reaction times. The catalyst could be separated using a simple magnetic extraction and reused 6 times with no remarkable loss of activity. The high activity of the prepared catalyst was attributed to the cooperative activation of the carbonyl group by both copper and cobalt via a synergistic catalytic effect that facilitates the Micheal addition of the hydroxyl group to the α,β-unsaturated ketone.     

Synthesis and Characterization of Magnetically Retrievable Fe3O4/Polyvinylpyrrolidone/Polystyrene Nanocomposite Catalyst for Efficient Catalytic Oxidation Degradation of Dyes Pollutants

Recently, the application of metal oxides such as Fe₃O₄ nanoparticles have wide interest for environmental remediation and treatment of wastewater especially contaminated with azo dyes owing to its high degradation efficacy and low toxicity. The recovery of magnetic catalysts without losing their efficiency is an essential feature in the catalytic applications. The aim of this article is to investigate and synthesis of magnetically retrievable Fe₃O₄/polyvinylpyrrolidone/polystyrene (Fe₃O₄/PVP/PS) nanocomposite for the catalytic degradation of azo dye acid red 18 (AR18). Fe₃O₄/PVP/PS nanocomposite was prepared in two steps. Firstly, PVP/PS microsphere was synthesized by γ-irradiation polymerization of styrene in presence of PVP solution. Secondly, deposition of Fe₃O₄ nanoparticles on PVP/PS microsphere was achieved by the alkaline co-precipitation of Fe³⁺/Fe²⁺ ions. The chemical structural and morphological properties of PVP/PS microsphere and Fe₃O₄/PVP/PS nanocomposite were examined by XRD, TEM, DLS, FTIR, EDX and VSM techniques. TEM results showed homogeneous morphology, spherical shaped and well-dispersed Fe₃O₄ nanoparticles with average particle size of 26 nm around PVP/PS microspheres. The VSM measurements of Fe₃O₄/PVP/PS nanocomposite exhibit excellent magnetic response of saturation magnetization 26.38 emu/g which is suitable in magnetic separation. The effect of the synthesized Fe₃O₄/PVP/PS nanocomposite on the catalytic degradation of AR18 in presence of hydrogen peroxide (H₂O₂) as a heterogeneous Fenton-like catalyst was examined. The catalyst Fe₃O₄/PVP/PS/H₂O₂ played basic role in promoting the oxidation degradation efficiency of AR18 of initial concentration 50 mg/L to 94.4% in 45 min with excellent recyclability till the sixth cycles under the best conditions of pH 3, 2% v/v H₂O₂ and 0.3 g catalyst amount. Furthermore, the Fe₃O₄/PVP/PS/H₂O₂ hybrid catalyst system supports high capability for oxidation degradation of mixture of different dyes. The Fe₃O₄/PVP/PS nanocomposite catalyst had high magnetic and recyclability characters which are acceptable for the treatment of wastewater contaminated by various dyes pollutants.

     

In-situ grown Ag on magnetic halloysite nanotubes in scaffolds: Antibacterial,biocompatibility and mechanical properties

A novel design of antibacterial and magnetic halloysite nanotubes loaded with Ag and Fe₃O₄ was reported. In detail, magnetic nanoparticles (Fe₃O₄) were immobilized on the surface of halloysite nanotubes (HNTs) via electrostatic adsorption (termed as HNTs/Fe₃O₄). The magnetic HNTs/Fe₃O₄ was then modified by polydopamine to in-situ grow Ag nanoparticles by a redox reaction, forming a composite nanostructure of HNTs/Fe₃O₄@Ag. The HNTs/Fe₃O₄@Ag was incorporated into poly-l-lactic acid (PLLA) scaffold fabricated via selective laser sintering, with the intent to endow the scaffold with robust antibacterial function and favorable cell activity. The results showed that the released Ag⁺ from the scaffold significantly against E. coli activity, with bacterial inhibition rate above 99%. Moreover, ion release behavior showed a scaffold enable to sustain release Ag⁺ over 28 days. Furthermore, Fe₃O₄ nanoparticles constructed magnetic microenvironment greatly enhanced cell activity and promoted cell proliferation. In addition, tensile strength of the scaffold increased by 52.9% compared with PLLA scaffold. These positive results suggested that the HNTs/Fe₃O₄@Ag nanostructure possessed potential in facilitating bone repair.     

Facile synthesis of magnetic Fe3O4@Chitosan nanocomposite as environmentally green catalyst in multicomponent Knoevenagel-Michael domino reaction

Magnetic Fe₃O₄ has interesting characteristics such as large surface area, low toxicity, ferromagnetic, and biocompatible. The presence of magnetic properties in Fe₃O₄ provides an advantage in its application as a heterogeneous catalyst. This study highlights the synthesis of Fe₃O₄ modified chitosan composite and evaluates the catalytic ability in multicomponent Knoevenagel-Michael domino reaction. The synthesis and characterization of pristine Fe₃O₄ and Fe₃O₄@Chi samples were investigated. The XRD analysis combined with refinement technique indicates that the pristine Fe₃O₄ crystallized in a cubic structure with Fd-3mz symmetry and the presence of chitosan in Fe₃O₄ sample did not change its structure. The FTIR analysis also demonstrated the binding of chitosan to the Fe₃O₄ nanoparticles. TEM image reveals the presence of chitosan in the composite sample formed a core-shell interaction and covered the surface of Fe₃O₄ nanoparticles. The evaluation of Fe₃O₄@Chi catalytic ability in multicomponent Knoevenagel-Michael domino reaction demonstrated reliable catalyst performance with a yield of 92.3% at optimum conditions. Fe₃O₄@Chi could be classified as a green catalyst because it can be used repeatedly with high yield and easy separation.     

Chitosan- and dehydroascorbic acid-coated Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles: preparation,characterization and their potential as draw solute in forward osmosis process

Forward osmosis (FO) is a natural osmosis process that has attracted a significant attention due to its many advantages. However, the development of FO process depends on the development of proper draw solutions. In this work, chitosan (CS)-coated Fe₃O₄ nanoparticles and dehydroascorbic acid (DHAA)-coated Fe₃O₄ nanoparticles were successfully synthesized by co-precipitation method and their performance as draw solutes was investigated for application in FO systems. CS and DHAA could improve the surface hydrophilicity of the Fe₃O₄ nanoparticles. The synthesized nanoparticles were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR) and vibrating sample magnetometry (VSM) which the results presented a small size, crystalline morphology and high magnetization value for their structure as well as a good dispersion in water. Cellulose triacetate/cellulose acetate (CTA/CA)-based membranes were also prepared by immersion precipitation and used as FO membranes. The synthesized FO membranes were characterized by FESEM. The performance evaluation of synthesized nanoparticles revealed that the water flux of Fe₃O₄ nanoparticles capped with DHAA was higher than that of the chitosan-coated Fe₃O₄ nanoparticles. At the end of the process, the Fe₃O₄ nanoparticles were easily separated from the diluted draw solution by applying the magnetic field.